The enhanced catalytic activity of PtRuRhNi was examined in relation to the oxidation of methanol in a direct methanol fuel cell. As evidenced by transmission electron microscopy and X-ray diffraction analysis, the synthesized PtRuRhNi appeared to be a well-synthesized Pt-based alloy nanoparticle. The catalytic activity of PtRuRhNi alloy electrocatalyst was superior to that of PtRu, from the standpoint of its high oxidation current, power density, and better stability in the electrochemical half- and single-cell measurements. Through X-ray absorption near edge structure and X-ray photoelectron spectroscopy, it was found that Pt and Ru in the PtRuRhNi are present in electronic and chemical states that are favorable to methanol electrooxidation. The dominant existence of Pt and Ru metallic states on the catalyst was essential for its high surface activity with respect to methanol electrooxidation. However, the catalytic enhancement of PtRuRhNi due to the chemical states of Rh/Ni was considered and examined. (C) 2004 Published by Elsevier Inc.